Upstream frame configuration for ethernet passive optical network protocol over coax (EPoC) networks

ABSTRACT

A method and system for generating upstream frames in an Ethernet Passive Optical Network protocol over Coax (EPoC) network is provided. Upstream frame configuration parameters are received by a CNU from a CLT in a link info broadcast a message. The CNU can recover the upstream frame configuration parameters from the link info broadcast message and generate at least in part upstream frame.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/950,054, filed Mar. 8, 2014, U.S. Provisional PatentApplication No. 61/981,549, filed Apr. 18, 2014, and U.S. ProvisionalPatent Application No. 62/001,569, filed May 21, 2014, all of which areincorporated herein by reference.

TECHNICAL FIELD

This application relates generally to Ethernet.

BACKGROUND

A Passive Optical Network (PON) includes a shared optical fiber andinexpensive optical splitters to divide the fiber into separate strandsfeeding individual subscribers. An Ethernet PON (EPON) is a PON based onthe Ethernet standard. EPONs provide simple, easy-to-manage connectivityto Ethernet-based, IP equipment, both at customer premises and at thecentral office. As with other Gigabit Ethernet media, EPONs arewell-suited to carry packetized traffic. An Ethernet Passive OpticalNetwork Protocol Over Coax (EPoC) is a network that enables EPONconnectivity over a coaxial network.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate the embodiments of the presentdisclosure and, together with the description, further serve to explainthe principles of the embodiments and to enable a person skilled in thepertinent art to make and use the embodiments.

FIG. 1 illustrates an example hybrid Ethernet Passive Optical Network(EPON)-Ethernet Passive Optical Network Over Coax (EPoC) networkarchitecture.

FIG. 2 illustrates another example hybrid EPON-EPoC networkarchitecture.

FIG. 3 illustrates an example EPoC portion of a hybrid EPON-EPoC networkaccording to an embodiment of the present disclosure.

FIG. 4 illustrates an exemplary EPoC network.

FIG. 5 illustrates an example of a PHY auto-negotiation and link upprocedure according to an embodiment of the present disclosure.

FIG. 6 illustrates an example upstream frame configuration according toan embodiment of the present disclosure.

FIG. 7 illustrates an example computer system that can be used toimplement aspects of the present disclosure.

The embodiments of the present disclosure will be described withreference to the accompanying drawings. The drawing in which an elementfirst appears is typically indicated by the leftmost digit(s) in thecorresponding, reference number.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the embodiments of thepresent disclosure. However, it will be apparent to those skilled in theart that the embodiments, including structures, systems, and methods,may be practiced without these specific details. The description andrepresentation herein are the common means used by those experienced orskilled in the art to most effectively convey the substance of theirwork to others skilled in the art. In other instances, well-knownmethods, procedures, components, and circuitry have not been describedin detail to avoid unnecessarily obscuring aspects of the disclosure.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

I. Example Hybrid EPON-EPoC Network Architectures

FIG. 1 illustrates an example hybrid Ethernet Passive Optical Network(EPON)-Ethernet Passive Optical Network Over Coax (EPoC) networkarchitecture 100 according to an embodiment of the present disclosure.As shown in FIG. 1, example network architecture 100 includes an OpticalLine Terminal (OLT) 102, an optional optical passive splitter 106, acommunications node 110 including a coaxial media converter (CMC) 112,an optional amplifier 116, an optional coaxial splitter 118, a coaxialnetwork unit (CNU) 122, and a plurality of subscriber media devices 124.

OLT 102 sits at a central office (CO) of the network and is coupled to afiber optic line 104. OLT 102 may implement a DOCSIS (Data Over CableService Interface Specification) Mediation Layer (DML) which allows OLT102 to provide DOCSIS provisioning and management of network components(e.g., CMC and Optical Network Unit (ONU)). Additionally, OLT 102implements an EPON Media Access Control (MAC) layer (e.g., IEEE802.3ah).

Optionally, optical passive splitter 106 can be used to split fiberoptic line 104 into a plurality of fiber optic lines 108. This allowsmultiple subscribers in different geographical areas to be served by thesame OLT 102 in a point-to-multipoint topology.

Communications node 110 serves as a converter between the EPON side andthe EPoC side of the network. Accordingly, communications node 110 iscoupled from the EPON side of the network to a fiber optic line 108 a,and from the EPoC side of the network to a coaxial cable 114. In anembodiment, communications node 110 includes a coaxial media converter(CMC) 112 that allows EPON to EPoC (and vice versa) conversion.

CMC 112 performs physical layer (PHY) conversion from EPON to EPoC, andvice versa. In an embodiment, CMC 112 includes a first interface (notshown in FIG. 1), coupled to fiber optic line 108, configured to receivea first optical signal from OLT 102 and generate a first bitstreamhaving a first physical layer (PHY) encoding. In an embodiment, thefirst PHY encoding is EPON PHY encoding. CMC 112 also includes a PHYconversion module (not shown in FIG. 1), coupled to the first interface,configured to perform PHY layer conversion of the first bitstream togenerate a second bitstream having a second PHY encoding. In anembodiment, the second PHY encoding is EPoC PHY encoding. Furthermore,CMC 112 includes a second interface (not shown in FIG. 1), coupled tothe PHY conversion module and to coaxial cable 114, configured togenerate a first radio frequency (RF) signal from the second bitstreamand to transmit the first RF signal over coaxial cable 114.

In EPoC to EPON conversion (i.e., in upstream communication), the secondinterface of CMC 112 is configured to receive a second RF signal fromCNU 122 and generate a third bitstream therefrom having the second PHYencoding (e.g., EPoC PHY encoding). The PHY conversion module of CMC 112is configured to perform PHY layer conversion of the third bitstream togenerate a fourth bitstream having the first PHY encoding (e.g., EPONPHY encoding). Subsequently, the first interface of CMC 112 isconfigured to generate a second optical signal from the fourth bitstreamand to transmit the second optical signal to OLT 102 over fiber opticline 108.

Optionally, an amplifier 116 and a second splitter 118 can be placed inthe path between communications node 110 and CNU 122. Amplifier 116amplifies the RF signal over coaxial cable 114 before splitting bysecond splitter 118. Second splitter 118 splits coaxial cable 114 into aplurality of coaxial cables 120, to allow service over coaxial cables ofseveral subscribers which can be within the same or different geographicvicinities.

CNU 122 generally sits at the subscriber end of the network. In anembodiment, CNU 122 implements an EPON MAC layer, and thus terminates anend-to-end EPON MAC link with OLT 102. Accordingly, CMC 112 enablesend-to-end provisioning, management, and Quality of Service (QoS)functions between OLT 102 and CNU 122. CNU 122 also provides multipleEthernet interfaces that could range between 10 Mbps to 10 Gbps, toconnect subscriber media devices 124 to the network. Additionally, CNU122 enables gateway integration for various services, including VOIP(Voice-Over-IP), MoCA (Multimedia over Coax Alliance), HPNA (HomePhoneline Networking Alliance), Wi-Fi (Wi-Fi Alliance), etc. At thephysical layer. CNU 122 may perform physical layer conversion fromcoaxial to another medium, while retaining the EPON MAC layer.

According to embodiments, EPON-EPoC conversion can occur anywhere in thepath between OLT 102 and CNU 122 to provide various serviceconfigurations according to the services needed or infrastructureavailable to the network. For example, CMC 112, instead of beingintegrated within node 110, can be integrated within OLT 102, withinamplifier 116, or in an Optical Network Unit (ONU) located between OLT102 and CNU 122 (not shown in FIG. 1). When CMC 112 is implemented inOLT 102 at the CO hub, OLT 102 may be more aptly referred to as a CableLine Terminal (CLT).

FIG. 2 illustrates another example hybrid EPON-EPoC network architecture200 according to an embodiment of the present disclosure. In particular,example network architecture 200 enables simultaneous FTTH (Fiber to theHome) and multi-tenant building EPoC service configurations.

Example network architecture 200 includes similar components asdescribed above with reference to example network architecture 100,including an OLT 102 located in a CO hub, a passive splitter 106, a CMC112, and one or more CNUs 122. OLT 102, splitter 106, CMC 112, and CNU122 operate in the same manner described above with reference to FIG. 1.

CMC 112 sits, for example, in the basement of a multi-tenant building204. As such, the EPON side of the network extends as far as possible tothe subscriber, with the EPoC side of the network only providing shortcoaxial connections between CMC 112 and CNU units 122 located inindividual apartments of multi-tenant building 204.

Additionally, example network architecture 200 includes an OpticalNetwork Unit (ONU) 206. ONU 206 is coupled to OLT 102 through anall-fiber link, comprised of fiber lines 104 and 108 c. ONU 206 enables.FTTH service to a home 202, allowing fiber optic line 108 c to reach theboundary of the living space of home 202 (e.g., a box on the outsidewall of home 202).

Accordingly, example network architecture 200 enables an operator toservice both ONUs and CNUs using the same OLT. This includes end-to-endprovisioning, management, and QoS with a single interface for both fiberand coaxial subscribers. In addition, example network architecture 200allows for the elimination of the conventional two-tiered managementarchitecture, which uses media cells at the end user side to manage thesubscribers and an OLT to manage the media cells.

II. Example Coaxial EPoC Link

FIG. 3 illustrates an example implementation 300 of an EPoC portion of ahybrid EPON-EPoC network. Example implementation 300 may be anembodiment of the EPoC portion of example EPON-EPoC network 100,described in FIG. 1, or example EPON-EPoC network 200, described abovein FIG. 2. As shown in FIG. 3, the EPoC portion includes an EPoC CMC 112and an EPoC CNU 122, connected via a coaxial network 304.

EPoC CMC 112 includes an optical transceiver 308, aserializer-deserializer (SERDES) 310, an EPoC PHY 312, including, in anembodiment, a CMC 314 and a modulator/demodulator 316, a controller 318,an analog-to-digital converter (ADC) 322, digital-to-analog converters(DAC) 320, and an radio frequency (RF) transceiver 326, including RFtransmit (TX) circuitry 336 and RF receive (RX) circuitry 338.

Optical transceiver 308 may include a digital optical receiverconfigured to receive an optical signal over a fiber optic cable 302coupled to CMC 112 and to produce an electrical data signal therefrom.Fiber optic cable 302 may be part of an EPON network that connects CMC112 to an OLT, such as OLT 102. Optical transceiver 307 may also includea digital optical laser to produce an optical signal from an electricaldata signal and to transmit the optical signal over fiber optic cable302.

SERDES 310 performs parallel-to-serial and serial-to-parallel conversionof data between optical transceiver 308 and EPoC PHY 312. Electricaldata received from optical transceiver 308 is converted from serial toparallel for further processing by EPoC PHY 312. Likewise, electricaldata from EPoC PHY 312 is converted from parallel to serial fortransmission by optical transceiver 308.

EPoC PHY 312, optionally with other modules of CMC 112, forms a two-wayPHY conversion module. In the downstream direction (i.e., traffic to betransmitted to EPoC CNU 122), EPoC PHY 312 performs PHY level conversionfrom EPON PHY to coaxial PHY and spectrum shaping of downstream traffic.For example, CMC interface 314 may perform line encoding functions,Forward Error Correction (FEC) functions, and framing functions toconvert EPON PHY frames into EPoC PHY frames for downstreamtransmissions to CNU 122, Modulator/demodulator 316 may modulate thedata received from SERDES 310 using either a single carrier ormulticarrier modulation technique (e.g., orthogonal frequency divisionmultiplexing (OFDM), orthogonal frequency division multiple access(OFDMA), sub-band division multiplexing, etc.). When using amulticarrier technique modulator/demodulator 316 can performmulticarrier functions, including determining sub-carriers fordownstream transmission, determining the width and frequencies of thesub-carriers, selecting the modulation order for downstreamtransmission, and dividing downstream traffic into multiple streams eachfor transmission onto a respective sub-carrier of the sub-carriers. Inthe upstream direction (i.e., traffic received from EPoC CNU 112), EPoCPHY 312 performs traffic assembly and PHY level conversion from coaxialPHY to EPON PHY. For example, modulator/demodulator 316 may assemblestreams received over multiple sub-carriers to generate a single stream.Then. CMC interface 314 may perform line encoding functions, FECfunctions, and framing functions to convert EPoC PHY frames into EPONPHY frames.

Controller 318 provides software configuration, management, and controlof EPoC PHY 312, including CMC interface 314 and modulator/demodulator316. In addition, controller 318 registers CMC 112 with the OLTservicing CMC 112. In an embodiment, controller 318 is an ONU chip,which includes an EPON MAC.

DAC 320 and ADC 322 sit in the data path between EPoC PHY 312 and RFtransceiver 326, and provide digital-to-analog and analog-to-digitaldata conversion, respectively, between EPoC PHY 312 and RF transceiver326.

RF transceiver 326 allows CMC 112 to transmit/receive RF signals overcoaxial network 304. In other embodiments, RF transceiver 326 may beexternal to CMC 112. RF TX circuitry 336 includes RF transmitter andassociated circuitry (e.g., mixers, frequency synthesizer, voltagecontrolled oscillator (VCO), phase locked loop (PLL), power amplifier(PA), analog filters, matching networks, etc.). RF RX circuitry 338includes RF receiver and associated circuitry (e.g., mixers, frequencysynthesizer, VCO, PLL, low-noise amplifier (LNA), analog filters, etc.).

EPoC CNU 122 includes RF transceiver 326, including RF TX circuitry 336and RF RX circuitry 338, DAC 320, ADC 322, an EPoC PHY 328, includingmodulator/demodulator 316 and a CNU interface 330, an EPoC MAC 332, anda PHY 334.

RF transceiver 326, DAC 320, ADC 322, and modulator/demodulator 316 maybe as described above with respect to EPoC CMC 112. Accordingly, theiroperation in processing downstream traffic (i.e., traffic received fromCMC 112) and upstream traffic (i.e., traffic to be transmitted to CMC112), which should be apparent to a person of skill in the art based onthe teachings herein, is omitted.

CNU interface 330 provides an interface between modulator/demodulator316 and EPON MAC 332. As such, CNU Interface 330 may perform coaxial PHYlevel decoding functions, including line decoding and FEC decoding, andframing functions to generate EPoC PHY frames for upstream transmission.EPON MAC 332 implements an EPON MAC layer, including the ability toreceive and process EPON Operation, Administration and Maintenance (OAM)messages, which may be sent by an OLT and forwarded by CMC 112 to CNU122. In addition, EPON MAC 332 interfaces with a PHY 334, which mayimplement an Ethernet PHY layer. PHY 334 enables physical transmissionover a user-network interface (UNI) 306 (e.g., Ethernet cable) to aconnected user equipment.

It should be noted that, in an alternate network configuration, CMC 112can be implemented within an OLT at the CO hub, such as within OLT 102shown in FIG. 1. In such an instance, it will be apparent to one ofordinary skill in the art that the implementation of CMC 112, shown inFIG. 3, can be modified to accommodate such a change. As noted above,when CMC 112 is implemented in an OLT, the OLT may be more aptlyreferred to as a Cable Line Terminal (CLT).

III. EPoC Auto-Negotiation and Link Up

The EPON standard defines an ONU registration procedure for pure EPONnetworks. This procedure is a MAC-level only procedure and thus is notsufficient to enable proper operation of an EPoC network. Specifically,the coaxial portion of an EPoC network requires an auto-negotiation todetermine the coaxial link spectrum, link bandwidth, and power level,and to establish precise timing between the CMC (or CLT) and the CNU.For example, in an EPON network, a link is designed to work at 1 Gbps or10 Gbps. In an EPoC network, the coaxial link will likely be limited toa lower bandwidth, which needs to be discovered before the link can beused. In addition, this auto-negotiation must not violate the EPONstandard, which governs MAC-level interaction.

In the following, a PHY auto-negotiation and link up procedure for anexemplary EPoC network 400 illustrated in FIG. 4 is described. The PHYauto-negotiation and link up procedure is preferably compliant with theEPON standard and is performed between a CMC (or CLT) EPoC PHY 402 andCNU EPoC PHYs 404 over (at least) a shared coaxial medium 406. The PHYauto-negotiation and link up procedure can be further used to enableperiodic maintenance of the links between the CMC (or CLT) EPoC PHY 402and the CNU EPoC PHYs 404. CMC EPoC PHY 402 can be implemented in a CMCsimilar to CMC 112, and one or more of CNU EPoC PHYs 404 can beimplemented in CNUs similar to CNU 122 described above with reference toFIG. 3.

Referring now to FIG. 5, an example of the PHY auto-negotiation and linkup procedure 500 is illustrated. As shown in FIG. 5, the procedure 500begins at step 502, which includes the CMC (or CLT) EPoC PHY 402periodically broadcasting a link info message over the coaxial medium406 to the CNU EPoC PHYs 404. As mentioned above, data is generallytransmitted over an EPoC network using a multi-carrier or multi-channeltransmission technique, such as orthogonal frequency divisionmultiplexing (OFDM) or orthogonal frequency division multiple access(OFDMA). The CMC (or CLT) EPoC PHY 402 is configured to broadcast thelink info message over one or more carriers or channels, collectivelyreferred to as the downstream PHY link channel, of the EPoC transmissionspectrum. This downstream PHY link channel is dedicated to carrying PHYauto-negotiation and link information (and no MAC-level data) to limitinterference with the MAC-level operation of the network.

The link info broadcast message can include several pieces of linkinformation. For example, the link info broadcast message can providelink information regarding the modulation mode used and the duplexingmode used (e.g. time division duplexing or frequency divisionduplexing). If the modulation used is multicarrier modulation, the linkinformation can further include the configuration of sub-carriers in theEPoC spectrum used to carry MAC-level data and control messages in theupstream and/or downstream direction. This configuration information caninclude all (or some) of the information required for the CNU PHY to beable to receive MAC-level data and control messages. For example, theconfiguration information can include the location in the EPoC spectrumof active downstream and upstream sub-carriers, the total number ofsub-carriers, which sub-carriers carry data and/or pilots, and thesub-carriers respective modulation orders, as well as the location ofany inactive sub-carriers in the EPoC spectrum. The link info broadcastmessage can further provide possible PHY configurations andcapabilities, including an interleaver depth and a forward errorcorrection type and size. In addition, when the downstream PHY linkchannel is used to convey timing information, it can carry time stampinformation. In addition, the downstream PHY link channel can be used tocarry power management messages. In this case, the downstream PHY linkchannel can carry information on wake-up times and modes, or moving intostandby or sleeping mode, for each of the CNUs using unicast orbroadcast messages. In addition, where OFDM is used to encode datatransmitted in either the downstream or upstream direction, theconfiguration information can include, in addition to the parametersalready mentioned, the number of sub-carriers per OFDM symbol, thecenter frequency of the sub-carriers that make up OFDM symbols, and thesize of any cyclic prefix added to OFDM symbols.

In step 506, unlinked ones of the CNU EPoC PHYs 404 are configured to“hunt” in the EPoC spectrum to locate the downstream PHY link channeland receive the link info broadcast message transmitted by the CMC (orCLT) EPoC PHY 402. The unlinked ones of the CNU EPoC PHYs 404 can “hunt”in the EPoC spectrum, for example, by looking for a predeterminedpreamble or bit pattern transmitted by the CMC (or CLT) EPoC PHY 402 atvarious frequencies to identify the downstream PHY link channel.

After unlinked ones of the CNU EPoC PHYs 404 locate the downstream PHYlink channel and receive/decode the link info broadcast message from theCMC (or CLT) EPoC PHY 402, the unlinked ones of the CNU EPoC PHYs 404can respond to the link info broadcast message using, for example, anecho protocol to perform auto negotiation and link up. An echo protocolcan be used to provide a mechanism to share access to the coaxial medium406 in the upstream direction between the unlinked ones of the CNU EPoCPHYs 404. For example, in the event that two or more unlinked ones ofthe CNU EPoC PHYs 404 attempt to respond to the link info broadcastmessage at the same time, the unlinked ones of the CNU EPoC PHYs 404 canimplement random back off times to resolve the contention.

At step 506, an unlinked one of the CNU EPoC PHYs 404 will respond tothe link info broadcast message by transmitting a reply message (e.g.,an “echo” or copy of the link info broadcast message) upstream to theCMC (or CLT) EPoC PHY 402. The reply message can include a preamble toallow the CMC (or CLT) EPoC PHY 402 to determine initial range timingand transmit power of the unlinked one of the CNU EPoC PHYs 404 and anaddress of the unlinked one of the CNU EPoC PHYs 404. The address of theunlinked one of the CNU EPoC PHYs 404 can be the Ethernet MAC address ofits associated CNU (or at least a portion of the Ethernet MAC address)or some other configurable address, for example. The reply message issent during an upstream PHY discovery window, which is described furtherbelow in regard to the upstream frame configuration shown in FIG. 6.

At step 508, the CMC (or CLT) EPoC PHY 402 receives and processes thereply message from the unlinked one of the CNU EPoC PHYs 404 and, usingthe address provided in the received message, sends a link configurationunicast message back to the unlinked one of the CNU EPoC PHYs 404. Thelink configuration unicast message can include additional configurationsettings to adjust, for example, the transmit power and a transmit delayof the unlinked one of the CNU EPoC PHYs 404.

More specifically, for the transmit delay, the CMC (or CLT) EPoC PHY 402can monitor the time it takes from the last link info broadcast messageit sends to the time it takes to receive the reply message from theunlinked one of the CNU EPoC PHYs 404 and, based on this time, determinean adjustment to the transmit delay in the unlinked one of the CNU EPoCPHYs 404. The adjustment can be determined to align upstream symboltransmissions from the unlinked one of the CNU EPoC PHYs 404 with theupstream symbol transmissions of the other CNU EPoC PHYs 404 operatingon the network. This adjustment value can be provided as a configurationsetting in the link configuration unicast message sent by the CMC (orCLT) EPoC PHY 402 over the downstream PHY link channel at step 508.

Similarly, for the transmit power setting, the CMC (or CLT) EPoC PHY 402can monitor the power level of the reply message received from theunlinked one of the CNU EPoC PHYs 404 and, based on this power level,determine an adjustment to the transmit power in the unlinked one of theCNU EPoC PHYs 404 to further optimize the data rate and/or bit-errorrate of the shared upstream channel. Again, this adjustment value can beprovided as a configuration setting in the link configuration unicastmessage sent by the CMC (or CLT) EPoC PHY 402 over the downstream PHYlink channel at step 508.

At step 510, the unlinked one of the CNU EPoC PHYs 404 receives anddecodes the link configuration unicast message and makes adjustments to,for example, its transmit power level and transmit delay based on thevalues in the decoded message. In addition, the unlinked one of the CNUEPoC PHYs 404 is configured to respond by transmitting a reply message(e.g., an “echo” or copy of the link configuration unicast message oranother appropriate response) upstream to the CMC (or CLT) EPoC PHY 402.The reply message includes status information of the unlinked one of theCNU EPoC PHYs 404. This status information can include, for example, anerror indicator or an indication of the power level of the messages theunlinked one of the CNU EPoC PHYs 404 is receiving from the CMC (or CLT)EPoC PHY 402. The reply message sent at step 510 can be sent over anupstream PHY link channel.

At step 512, the CMC (or CLT) EPoC PHY 402 receives and processes thereply message and status information sent by the unlinked one of the CNUEPoC PHYs 404 and responds by transmitting another link configurationunicast message over the DS PHY link channel. This link configurationunicast message can inform the unlinked one of the CNU EPoC PHYs 404 totransition to a linked state. For example, if the power level and symboltiming of the reply message to the link configuration unicast messagethe CMC (or CLT) EPoC PHY 402 receives at step 512 from the unlinked oneof the CNU EPoC PHYs 404 are acceptable, the CNU EPoC PHYs 404 can sendthe link configuration unicast message over the DS PHY link channel toinform the unlinked one of the CNU EPoC PHYs 404 to transition to alinked state. Otherwise, if the power level and symbol timing are notacceptable, CMC (or CLT) EPoC PHY 402 can go back to step 508 and sendanother link configuration unicast message to the unlinked one of theCNU EPoC PHYs 404 to adjust the transmit power and/or the transmit delayof the unlinked one of the CNU EPoC PHYs 404.

Assuming that the CMC (or CLT) EPoC PHY 402 sent a link configurationunicast message to the unlinked one of the CNU EPoC PHYs 404 to informit to transition to a linked state at step 512, at step 514 the unlinkedone of the CNU EPoC PHYs 404 can respond to this message by transmittinga reply message (e.g., an “echo” or copy of the link configurationunicast message it just received) upstream to the CMC (or CLT) EPoC PHY402. The reply message includes status information indicating that theunlinked one of the CNU EPoC PHYs 404 is now linked and ready totransmit and receive EPON MAC-level messages. The reply message can besent upstream over the upstream PHY link channel, which is describedfurther below in regard to the upstream frame configuration shown inFIG. 6.

It should be noted that after (or even before) a CNU EPoC PHY has beenlinked, a GMC (or CLT) EPoC PHY can continue to transmit linkconfiguration unicast messages to the linked CNU EPoC PHY (and inresponse receive a reply message from the linked CNU EPoC PHY) todetermine if any further or additional adjustments need to be made tothe configuration settings of the linked CNU EPoC PHY. For example,after having been linked (or even before), adjustments can be made tothe transmit power and/or transmit delay of the CNU EPoC PHY. Otheradjustments can be made to coefficients of a pre-equalizer at the CNUEPoC PHY used to pre-equalize upstream transmissions before thetransmissions are sent to the CMC (or CLT) EPoC PHY.

IV. EPoC Network Upstream Frame Configuration

Upstream transmissions from the CNU EPoC PHYs 404 to the CMC (or CLT)EPoC PHY 402, including the reply messages described above in regard toFIG. 5 and MAC-level data, are organized into upstream frames thatcyclically repeat. The exact configuration of these frames is determinedin part by the link information included in the link info broadcastmessage received by the CNU EPoC PHYs 404 from the CMC (or CLT) EPoC PHY402 at step 506 as described above in regard to FIG. 5.

FIG. 6 illustrates an exemplary configuration of an upstream frame 600used in an EPoC network. Upstream frame 600 includes two types ofsub-frames: a probe frame that spans P OFDMA symbols in time followed byNf data frames that each span M OFDMA symbols in time, where P, Nf, andM are integers. The spectrum of upstream frame 600 spans Ns OFDMAsubcarriers where, in one embodiment. Ns is equal to the number ofsubcarriers in a single upstream OFDMA symbol. In one embodiment, thevalue of Ns is provided to the CNU EPoC PHYs 404 via the linkinformation in the link info broadcast message as described above inregard to step 506 in FIG. 5. Further details on the specific structureof the Nf data frames and the probe frame are described further below inturn.

In one embodiment, the Nf data frames have a fixed length in terms ofOFDMA symbols of 256 and each of the Nf data frames has either M=8 orM=16 OFDMA symbols. Assuming each of the Nf data frames has M=8 OFDMAsymbols, the number of data frames in upstream frame 600 is given byNf=256/8 or 32. If, on the other hand, each of the Nf data frames hasM=16 OFDMA symbols, the number of data frames in upstream frame 600 isgiven by Nf=256/16 or 16. In one embodiment, either the number of dataframes Nf (i.e., either 32 or 16) or the number of OFDMA symbols M ineach data frame (i.e., either 8 or 16) is provided to the CNU EPoC PHYs404 via the link information in the link info broadcast message asdescribed above in regard to step 506 in FIG. 5. In other embodiments,the Nf data frames can have a different fixed length in terms of OFDMAsymbols other than 256 and/or the Nf data frames can have a differentnumber M of OFDMA symbols other than 8 or 16.

As further shown in FIG. 6, each data frame is further broken down intoa column of resource blocks that each span the M OFDMA symbols in timebut only a single OFDMA subcarrier in spectrum. In one embodiment, thenumber of OFDMA symbols M in each resource block is provided to the CNUEPoC PHYs 404 via the link information in the link info broadcastmessage as described above in regard to step 506 in FIG. 5.

Resource blocks can carry MAC-level data or data associated with theupstream PHY link channel. The upstream PHY link channel can be used bythe CNU EPoC PHYs 404 to transmit reply messages upstream to the CMC (orCLT) EPoC PHY 402. For example, the upstream PHY link channel can beused by the CNU EPoC PHYs 404 to transmit the reply messages at steps510 and 512 in FIG. 5 described above. In one embodiment, the upstreamPHY link channel occupies 8 adjacent resource blocks from each of the Nfdata frames and does not extend into the probe frame. In anotherembodiment, the specific number and/or location of the resource blocksthat the upstream PHY link channel occupies within the Nf data frames isprovided to the CNU EPoC PHYs 404 via the link information in the linkinfo broadcast message as described above in regard to step 506 in FIG.5.

All remaining resource blocks from the Nf data frames not assigned to oroccupied by the upstream PHY link channel can be used by the CNU EPoCPHYs 404 to transmit MAC-level data upstream to the CIVIC (or CLT) EPoCPHY 402. In one embodiment, the CMC (or CLT) EPoC PHY 402 can assigneach resource block within a data frame not assigned to or occupied bythe upstream PHY link channel to any one of the CNU EPoC PHYs 404 totransmit MAC-level data upstream. In addition, the CMC (or CLT) EPoC PHY402 can assign, on a per resource block basis, a constellation size forthe symbols to be transmitted over the associated subcarrier of theresource block. The constellation size determines the number of bits (orbit-loading) carried by the symbols transmitted over a sub-carrier. Forexample, a QAM symbol with a 64 point constellation can carry 6-bits ofinformation. In one embodiment, the constellation size assignments isprovided to the CNU EPoC PHYs 404 via the link information in the linkinfo broadcast message as described above in regard to step 506 in FIG.5.

Referring now to the probe frame, in one embodiment the probe frame hasa fixed length in terms of OFDMA symbols of 6. The probe frame caninclude one or more of a PHY discovery window, a fine ranging window,and a probe region.

The PHY discovery window was mentioned above in regard to FIG. 5. Inparticular, the PHY discovery window is a portion of the probe frameduring which unlinked ones of the CNU EPoC PHYs 404 can send a replymessage upstream to the CMC (or CLT) EPoC PHY 402 to allow the CMC (orCLT) EPoC PHY 402 determine initial range timing and transmit power ofthe unlinked one of the CNU EPoC PHYs 404 and an address of the unlinkedone of the CNU EPoC PHYs 404. The reply message can specifically includea preamble to allow the CMC (or CLT) EPoC PHY 402 to determine initialrange timing and transmit power of the unlinked one of the CNU EPoC PHYs404. The CNU EPoC PHYs 404 can subsequently adjust the transmit powerand transmit delay of the unlinked one of the CNU EPoC PHYs 404 based onthe determined initial range timing and transmit power. In oneembodiment, the specific region of the probe frame that the upstream PHYdiscovery window occupies is provided to the CNU EPoC PHYs 404 via thelink information in the link info broadcast message as described abovein regard to step 506 in FIG. 5.

After the CMC (or CET) EPoC PHY 402 performs initial ranging anddetermines the address of one of the CNU EPoC PHYs 404, the CMC (or CLT)EPoC PHY 402 can direct the one of the CNU EPoC PHYs 404 to transmitupstream during a fine ranging window to permit the CMC (or CLT) EPoCPHY 402 to determine fine adjustments of the transmit delay and/ortransmit power of the one of the CNU EPoC PHYs 404. In one embodiment,the specific region of the probe frame that the fine ranging windowoccupies is provided to the CNU EPoC PHYs 404 via the link informationin the link info broadcast message as described above in regard to step506 in FIG. 5. The CMC (or CLT) EPoC PHY 402 can assign a particular oneof the CNU EPoC PHYs 404 to transmit upstream during a fine rangingwindow using a unicast message to the particular one of the CNU EPoCPHYs 404.

The probe region of a probe frame is used by the CNU EPoC PHYs 404 totransmit known pilot patterns upstream to the CMC (or CLT) EPoC PHY 402.The CMC (or CLT) EPoC PHY 402 can use a received pilot pattern todetermine a response of the upstream channel between the one of the CNUEPoC PHYs 404 that transmitted the known pilot pattern and the CMC (orCLT) EPoC PHY 402. The channel estimate can then be used by the CMC (orCLT) EPoC PHY 402 to determine or adjust pre-equalization coefficientsof a pre-equalizer at the one of the CNU EPoC PHYs 404 to better matchthe channel response characteristics. In one embodiment, the specificregion of the probe frame that the probe region occupies is provided tothe CNU EPoC PHYs 404 via the link information in the link infobroadcast message as described above in regard to step 506 in FIG. 5.The CMC (or CLT) EPoC PHY 402 can assign a particular one of the CNUEPoC PHYs 404 to transmit upstream during at least a part of the proberegion using a unicast message to the particular one of the CNU EPoCPHYs 404.

The known pilots in the probe symbols (i.e., the symbols of the probeframe) can also be used to range CNUs in time offset and transmissionpower, for the fine ranging of new CNUs and for periodic maintenance ofexisting CNUs.

V. Example Computer System Environment

It will be apparent to persons skilled in the relevant art(s) thatvarious elements and features of the present disclosure, as describedherein, can be implemented in hardware using analog and/or digitalcircuits, in software, through the execution of instructions by one ormore general purpose or special-purpose processors, or as a combinationof hardware and software.

The following description of a general purpose computer system isprovided for the sake of completeness. Embodiments of the presentdisclosure can be implemented in hardware, or as a combination ofsoftware and hardware. Consequently, embodiments of the disclosure maybe implemented in the environment of a computer system or otherprocessing system. An example of such a computer system 700 is shown inFIG. 7. Modules depicted in FIGS. 1-4 may execute on one or morecomputer systems 700. Furthermore, each of the steps of the processesdepicted in FIG. 5 can be implemented on one or more computer systems700.

Computer system 700 includes one or more processors, such as processor704. Processor 704 can be a special purpose or a general purpose digitalsignal processor. Processor 704 is connected to a communicationinfrastructure 702 (for example, a bus or network). Various softwareimplementations are described in terms of this exemplary computersystem. After reading this description, it will become apparent to aperson skilled in the relevant art(s) how to implement the disclosureusing other computer systems and/or computer architectures.

Computer system 700 also includes a main memory 706, preferably randomaccess memory (RAM), and may also include a secondary memory 708.Secondary memory 708 may include, for example, a hard disk drive 710and/or a removable storage drive 712, representing a floppy disk drive,a magnetic tape drive, an optical disk drive, or the like. Removablestorage drive 712 reads from and/or writes to a removable storage unit716 in a well-known manner. Removable storage unit 716 represents afloppy disk, magnetic tape, optical disk, or the like, which is read byand written to by removable storage drive 712. As will be appreciated bypersons skilled in the relevant art(s), removable storage unit 716includes a computer usable storage medium having stored therein computersoftware and/or data.

In alternative implementations, secondary memory 708 may include othersimilar means for allowing computer programs or other instructions to beloaded into computer system 700. Such means may include, for example, aremovable storage unit 718 and an interface 714. Examples of such meansmay include a program cartridge and cartridge interface (such as thatfound in video game devices), a removable memory chip (such as an EPROM,or PROM) and associated socket, a thumb drive and USB port, and otherremovable storage units 718 and interfaces 714 which allow software anddata to be transferred from removable storage unit 718 to computersystem 700.

Computer system 700 may also include a communications interface 720.Communications interface 720 allows software and data to be transferredbetween computer system 700 and external devices. Examples ofcommunications interface 720 may include a modem, a network interface(such as an Ethernet card), a communications port, a PCMCIA slot andcard, etc. Software and data transferred via communications interface720 are in the form of signals which may be electronic, electromagnetic,optical, or other signals capable of being received by communicationsinterface 720. These signals are provided to communications interface720 via a communications path 722. Communications path 722 carriessignals and may be implemented using wire or cable, fiber optics, aphone line, a cellular phone link, an RF link and other communicationschannels.

As used herein, the terms “computer program medium” and “computerreadable medium” are used to generally refer to tangible storage mediasuch as removable storage units 716 and 718 or a hard disk installed inhard disk drive 710. These computer program products are means forproviding software to computer system 700.

Computer programs (also called computer control logic) are stored inmain memory 706 and/or secondary memory 708. Computer programs may alsobe received via communications interface 720. Such computer programs,when executed, enable the computer system 700 to implement the presentdisclosure as discussed herein. In particular, the computer programs,when executed, enable processor 704 to implement the processes of thepresent disclosure, such as any of the methods described herein.Accordingly, such computer programs represent controllers of thecomputer system 700. Where the disclosure is implemented using software,the software may be stored in a computer program product and loaded intocomputer system 700 using removable storage drive 712, interface 714, orcommunications interface 720.

In another embodiment, features of the disclosure are implementedprimarily in hardware using, for example, hardware components such asapplication-specific integrated circuits (ASICs) and gate arrays.Implementation of a hardware state machine so as to perform thefunctions described herein will also be apparent to persons skilled inthe relevant art(s).

V. Conclusion

Embodiments have been described above with the aid of functionalbuilding blocks illustrating the implementation of specified functionsand relationships thereof. The boundaries of these functional buildingblocks have been arbitrarily defined herein for the convenience of thedescription. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the disclosure that others can, by applyingknowledge within the skill of the art, readily modify and/or adapt forvarious applications such specific embodiments, without undueexperimentation, without departing from the general concept of thepresent disclosure. Therefore, such adaptations and modifications areintended to be within the meaning and range of equivalents of thedisclosed embodiments, based on the teaching and guidance presentedherein. It is to be understood that the phraseology or terminologyherein is for the purpose of description and not of limitation, suchthat the terminology or phraseology of the present specification is tobe interpreted by the skilled artisan in light of the teachings andguidance.

What is claimed is:
 1. A coaxial network unit (CNU), comprising: a radiofrequency (RF) receiver configured to receive a plurality of messagesfrom a coaxial line terminal (CLT); and an Ethernet Passive OpticalNetwork over Coax (EPoC) physical layer (PHY) configured to recover linkinformation from at least one of the plurality of messages and generateat least a portion of an upstream frame in accordance with the recoveredlink information, the upstream frame comprising a probe frame followedin time by a plurality of data frames, wherein the recovered linkinformation comprises a time span allocation for resource blocks in theupstream frame in terms of orthogonal frequency division multiple access(OFDMA) symbols, an indication of a specific region of the probe frameoccupied by a PHY discovery window during which unlinked CNUs send replymessages upstream to the CLT, and an assignment of the resource blocksin the upstream frame to linked CNUs, and wherein the plurality of dataframes comprise an upstream PHY link channel for transmitting an echomessage to the CLT to complete a link up procedure between the CNU andthe CLT, the echo message comprising a copy of a link configurationunicast message received from the CLT.
 2. The CNU of claim 1, whereinthe probe frame has a time span allocation in terms of OFDMA symbols of6.
 3. The CNU of claim 1, wherein the plurality of data frames have atime span allocation in terms of OFDMA symbols of
 256. 4. The CNU ofclaim 1, wherein the plurality of data frames comprise the resourceblocks.
 5. The CNU of claim 4, wherein a first portion of the resourceblocks in each of the plurality of data frames carry data associatedwith the upstream PHY link channel and a second portion of the resourceblocks in each of the plurality of data frames carry Media AccessControl (MAC) level data.
 6. The CNU of claim 1, wherein the probe frameincludes a fine ranging window or a probe region.
 7. The CNU of claim 6,wherein the recovered link information indicates a specific region ofthe probe frame occupied by the fine ranging window or the probe region.8. The CNU of claim 6, wherein the PHY discovery window is used to carrya reply message from the CNU upstream to the CLT to allow the CLT todetermine initial range timing, transmit power, or an address of theCNU.
 9. The CNU of claim 6, wherein the probe region is used to carry apilot pattern from the CNU upstream to the CLT to allow the CLT todetermine or adjust pre-equalization coefficients of a pre-equalizer atthe CNU.
 10. The CNU of claim 1, wherein the time span allocation forresource blocks in the upstream frame is either 8 or 16 OFDMA symbols.11. A method for transmitting upstream frames over an Ethernet PassiveOptical Network protocol over Coax (EPoC) network, comprising: receivinga link info broadcast message from a coaxial line terminal (CLT);recovering link information from the link info broadcast message; andgenerating at least a portion of an upstream frame in accordance withthe recovered link information, the upstream frame comprising a probeframe followed in time by a plurality of data frames, wherein therecovered link information includes a time span allocation for resourceblocks in the upstream frame in terms of orthogonal frequency divisionmultiple access (OFDMA) symbols, an indication of a specific region ofthe probe frame occupied by a PHY discovery window during which unlinkedcoaxial network units (CNUs) send reply messages upstream to the CLT,and an assignment of the resource blocks in the upstream frame to linkedCNUs, and wherein the plurality of data frames comprise an upstream PHYlink channel for transmitting an echo message to the CLT to complete alink up procedure, the echo message comprising a copy of a linkconfiguration unicast message received from the CLT.
 12. The method ofclaim 11, wherein the probe frame has a time span allocation in terms ofOFDMA symbols of 6 and the plurality of data frames have a time spanallocation in terms of OFDMA symbols of
 256. 13. The method of claim 11,wherein probe symbols in the probe frame are used to range the CNUs intime offset and transmission power and to set pre-equalizationcoefficients for the CNUs.
 14. The method of claim 11, wherein theplurality of data frames include the resource blocks.
 15. The method ofclaim 14, wherein a first portion of the resource blocks in each of theplurality of data frames carry data associated with the upstream PHYlink channel and a second portion of the resource blocks in each of theplurality of data frames carry Media Access Control (MAC) level data.16. The method of claim 11, wherein the probe frame includes a fineranging window or a probe region.
 17. The method of claim 16, whereinthe recovered link information indicates a specific region of the probeframe occupied by the fine ranging window or the probe region.
 18. Amethod for transmitting upstream frames over an Ethernet Passive OpticalNetwork protocol over Coax (EPoC) network, comprising: receiving a linkinfo broadcast message from a coaxial line terminal (CLT); recoveringlink information from the link info broadcast message; generating aportion of an upstream frame in accordance with the recovered linkinformation, the upstream frame comprising a probe frame followed intime by a plurality of data frames; and transmitting the portion of theupstream frame to the CLT over the EPoC network, wherein the recoveredlink information includes a time span allocation for resource blocks inthe upstream frame in terms of orthogonal frequency division multipleaccess (OFDMA) symbols, an indication of a specific region of the probeframe occupied by a PHY discovery window during which unlinked coaxialnetwork units (CNUs) send reply messages upstream to the CLT, and anassignment of the resource blocks in the upstream frame to linked CNUs,and wherein the plurality of data frames comprise an upstream PHY linkchannel for transmitting an echo message to the CLT to complete a linkup procedure, the echo message comprising a copy of a link configurationunicast message received from the CLT.
 19. The method of claim 18,wherein the probe frame has a time span allocation in terms of OFDMAsymbols of 6 and the plurality of data frames have a time spanallocation in terms of OFDMA symbols of
 256. 20. The method of claim 18,wherein probe symbols in the probe frame are used to range the CNUs intime offset and transmission power and to set pre-equalizationcoefficients for the CNUs.